• Title/Summary/Keyword: Red-X

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CHARACTERIZATION OF $YBa_2Cu_3O_{7-x}$ MADE BY A SOL-GEL PROCESS USING NITRATE SALTS AND SODIUM HYDROXIDE (질산염(窒酸鹽)과 수산화(水酸化)나트륨을 써서 졸-겔 법(法)으로 만든 $YBa_2Cu_3O_{7-x}$의 특성분석(特性分析))

  • Kim, Bong-Heup;Kang, Hyung-Boo;Kim, Hyun-Teak
    • Proceedings of the KIEE Conference
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    • 1990.11a
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    • pp.143-149
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    • 1990
  • A sol-gel processing of $YBa_2Cu_3O_{7-x}$ superconductor using metal nitrate salts and sodium hydroxide as the starting materials has been investigated because of the need to produce pure, hompgeneous superconducting materials. Since the precipitation of barium hydroxides can be obtained only at high basicities, the process has to be carried out Ca. pH 13 to get the simultaneous coprecipitation with the other metal hydroxides. The involved reaction mechanisms were investigated and intermediate and final products were characterized by means of thermogravimetric analysis(TGA), infra-red(IR) spectroscopy, X-ray diffraction(XRD) analysis, scanning electron microscopy(SEM), thermal mechanical analysis(TMA) and electrical measurement.

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A Experimental Study on Attenuation Rate of Construction Materials in the Diagnostic X-ray Energy (진단 영역의 X-선 에너지에서 각종 건축재료의 감약율 측정실험)

  • Kim, Jung-Min;Jung, Hoi-Won
    • Journal of radiological science and technology
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    • v.21 no.2
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    • pp.11-18
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    • 1998
  • Single phase, narrow beam X-ray attenuation data were obtained using various construction materials concrete, white block, red block, 3 hole block, gypsum board, artificial marble, cement, plate glass, wood, and lead. Tube voltages of 60, 80, 100, 120 kVp were employed and the resulting curves were compared to transmission data found in this report. The shielding methodology and the derivation of equations used for determination of barrier requirements were presented in NCRP 49. We could calculate the X-ray exposed dose after attenuation and thickness of protection barrier in the clinic facilities accordingly. For the purpose of maximizing the benefit/cost ratio to diagnostic shielding, various construction materials must be installed carefully and attnuation rate considered thoroughly.

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Preparation and Photoluminescence Properties of $Ba_{1-x}M_xGa_2S_4:Eu^{2+}$ (M = Ca, Sr) Phosphor

  • Yoo, Hyoung-Sun;Kim, Sung-Wook;Han, Ji-Yeon;Park, Bong-Je;Jeon, Duk-Young
    • 한국정보디스플레이학회:학술대회논문집
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    • 2008.10a
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    • pp.561-564
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    • 2008
  • $Ba_{1-x}M_xGa_2S_4:Eu^{2+}$ (M = Ca, Sr) phosphor was prepared for white light emitting diodes application. Photoluminescence (PL) emission and excitation bands were red-shifted with increase of Ca and Sr content due to the crystal field effect. Moreover, the PL intensity under 450 nm was increased by substitution of Ca and Sr.

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Enhanced Luminescence of $SrTiO_3:Pr^{3+}$by Incorporating with $Li^+$ or $Na^+$Ion

  • Tian, Lianhua;Mho, Sun-Il;Bae, Hyun-Sook;Yu, Byung-Yong;Pyun, Chong-Hong
    • 한국정보디스플레이학회:학술대회논문집
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    • 2002.08a
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    • pp.819-821
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    • 2002
  • Photoluminescenc (PL) and low-voltage cathodoluminescence (CL) characteristics of $[xSrTiO_3+(1-x)Li_2TiO_3]:Pr^{3+}$ and $[xSrTiO_3+(1-x)Na_2TiO_3]:Pr^{3+}$ systems were investigated. The red luminescence intensities of these compounds are enhanced remarkably by the incorporation of $Li^+$ or $Na^+$ ion as compared to that of $SrTiO_3:Pr^{3+}$. The enhanced luminescence is speculated to result from both the charge compensation of $Pr^{3+}$ site and oxygen vacancies generated in the lattices by $Li^+$ or $Na^+$ ion.

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Photoluminescence of Undoped and $Ho^{3+}-Doped ZnSe,\; Mg_{0.15}Zn_{0.85}$Se Single Crystals (ZnSe, $ZnSe:Ho^{+3}, Mg_{0.15}Zn_{0.85}Se\; 및 Mg_{0.15}Zn_{0.85}Se:Ho^{3+}$ 단결정의 광발광 특성에 관한 연구)

  • Kim, Nam-O;Kim, Hyeong-Gon;O, Geum-Gon
    • The Transactions of the Korean Institute of Electrical Engineers C
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    • v.50 no.9
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    • pp.434-437
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    • 2001
  • ZnSe, ZnSe:Ho/sup 3+/, Mg/sub x/Zn/sub 1-x/Se and Mg/sub x/Zn/sub 1-x/Se:Ho/sup 3+/ crystals were grown by the chemical transport reaction method. The crystal structures and optical energy band gaps of the single crystals were investigated. Their photoluminescence(PL) spectra were measured at 10 [K]. Sharp emission peaks in the blue-green wavelength range and broad emission peaks in the yellow-red wavelength range were observed. The single crystals doped with 1.0 [mol%] of holmium did not show the sharp emission peaks because of defects which were thought to be originated to the holmium dopant.

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Synthesis of $Y_2$$O_3$:$^Eu{3+}$ Phosphor for Low-voltage by Polymerized Complex Method (착체중합법에 의한 저전압용 $Y_2$$O_3$: $Eu^{3+}$ 형광체 제조)

  • 류호진;박정규;박희동
    • Journal of the Korean Ceramic Society
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    • v.35 no.8
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    • pp.801-806
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    • 1998
  • $Eu^{3+}$ -doped $Y_2$$O_3$ phosphors has been prepared by a polymerized complex method and investigated their powder and luminescence properties. They were compared with phosphors prepared by a solid state reac-thion method. The phosphors synthesized have been characterized by X-ray diffraction low-voltage lu-minescent emission spectroscopy etc. Under low-voltage electron excitation $Eu^{3+}$-doped $Y_2$$O_3$ exhibited a strong narrow-band red emission peaking at 612nm. On the other hand the critical value for concentration quenching of sample prepared by the polymerized complex method fired at $1400^{\circ}C$ is x=0.05 for $(Y_{1-x}Eu_x__2O_3$ The emission intensity of phosphors prepared by the polymerized complex method was higher than that of phosphors prepared by the solid state reaction method.

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Synthesis and Design of Electroactive Polymers for Improving Efficiency and Thermal Stability in Organic Photovoltaics

  • Kim, Beom-Jun
    • Proceedings of the Materials Research Society of Korea Conference
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    • 2011.05a
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    • pp.11.2-11.2
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    • 2011
  • Polymer based organic photovoltaics have attracted a great deal of attention due to the potential cost-effectiveness of light-weight and flexible solar cells. However, most BHJ polymer solar cells are not thermally stable as subsequent exposure to heat drives further development of the morphology towards a state of macrophase separation in the micrometer scale. Here we would like to show three different approaches for developing new electroactive polymers to improve the thermal stability of the BHJ solar cells, which is a critical problem for the commercialization of these solar cells. For one of the examples, we report a new series of functionalized polythiophene (PT-x) copolymers for use in solution processed organic photovoltaics (OPVs). PT-x copolymers were synthesized from two different monomers, where the ratio of the monomers was carefully controlled to achieve a UV photo-crosslinkable layer while leaving the ${\pi}-{\pi}$ stacking feature of conjugated polymers unchanged. The crosslinking stabilizes PT-x/PCBM blend morphology preventing the macro phase separation between two components, which lead to OPVs with remarkably enhanced thermal stability. The drastic improvement in thermal stabilities is further characterized by microscopy as well as grazing incidence X-ray scattering (GIXS). In the second part of talk, we will discuss the use of block copolymers as active materials for WOLEDs in which phosphorescent emitter isolation can be achieved. We have exploited the use of triarylamine (TPA) oxadiazole (OXA) diblock copolymers (TPA-b-OXA), which have been used as host materials due to their high triplet energy and charge-transport properties enabling a balance of holes and electrons. Organization of phosphorescent domains in TPA-b-OXA block copolymers is demonstrated to yield dual emission for white electroluminescence. Our approach minimizes energy transfer between two colored species by site isolation through morphology control, allowing higher loading concentration of red emitters with improved device performance. Furthermore, by varying the molecular weight of TPA-b-OXA and the ratio of blue to red emitters, we have investigated the effect of domain spacing on the electroluminescence spectrum and device performance.

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Luminescence Characteristics and Crystal Structure of CaWO4-Li2WO4-Eu2O3 Phosphors (CaWO4-Li2WO4-Eu2O3계 형광체의 PL 특성과 결정구조)

  • Kim, Jeong-Seog;Choi, Jin-Ho;Jeong, Bong-Man;Kang, Hyun-Ju
    • Journal of the Korean Ceramic Society
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    • v.43 no.1 s.284
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    • pp.10-15
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    • 2006
  • Photoluminescence (PL) and crystal structures of the $(l-x)CaWO_4-xLi_2WO_4$ binary system added with $Eu_2O_3$ activator have been characterized. The $CaWO_4\;and\;Li_2WO_4$ have the scheelite and phenakite structures respectively. The $CaWO_4-Li_2WO_4-Eu_2O_3$ phosphors show the red luminescence of 613 nm peak wavelength. The wavelength range of excitation spectral band is $380\~470$ nm with the peak wavelength of 397 nm. The $0.88(0.5CaWO_4-0.5Li_2WO_4)-0.12Eu_2O_3$ showed the most superior luminescence characteristics. The effect of co-doping elements such as $Al_2O_3$ and rare-earth oxides on PL has been characterized. The co-doping elements deteriorated the luminescence intensity except the $Al_2O_3$ and $Gd_2O_3$. The PL characteristics of $CaWO_4-Li_2WO_4-Eu_2O_3$ phosphors have been compared to those of the alkali europium double molybdates (tungstates) of scheelite-related structure such as $LiEu(MoO_4)_2$ and $CsEu(MoO_4)_2$. The crystal structures of $(l-y)[(l-x)CaWO_4-xLi_2WO_4]-yEu_2O_3$ phosphors have been characterized using XRD data and rietveld refinement.

A study on the fruit color characteristics and persisting period of deciduous woody landscape plants in Middle area of Korea (중부지방 낙엽조경수목의 열매색 특성 및 지속 기간에 관한 연구)

  • 서병기;심경구;정해준;심재성
    • Journal of the Korean Institute of Landscape Architecture
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    • v.23 no.3
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    • pp.144-154
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    • 1995
  • The fruit color characteristics and persisting period of deciduous woody landscape plants were investigated through the field survey in Suwon region from January 1, 1992 to March 20, 1993. The summary of the study results was as follows; The total fruit color persisting period was about 320 days from May 1, 1992 when Prunus mume was beginning of fruit coloring, to March 20, 1993 when the fruits of Platanus occidentalis and platanus X acerifolia were persisting. And the plants of fruit persisting period over 60 days after leaf falling were Vibumum erosum, Ilex serrata, Ilex verticillata 'Christmas Cheer', Platanus X acerifolia, Platanus occidentalis, Berberis thunbergii 'Atropupurea', Ligustrum obtusifolium. According to the KBS standard color number, 52.6% of of the fruit color were red, 18.9% yellow, 11.6% black, green 9.5%, white 2.1%, violet 1.1%, and red is followed black 4.2%. Evodia daniellii, Ilex verticillata 'Christmas Cheer', Ilex serrata, Ginkgo biloba, Lindera obtusiloba, and Lindera erythrocarpa should be planted male and female species together for fruits. We got the new information on the fruit color characteritics and persisting period of Malus 'Hopa', Malus 'Almey', Malus 'Pioneer X', Acer rubrum, Malus prunifolia, Pyrus serotina, Berberis thunbergii 'Atropurpurea', Vibumum rhytidophyllum, Rosa spp. Vitis vinifera, Vaccinium angustifolium, Ilex verticillata 'Christmas Cheer', Magnolia stellata, Aronia arbutifolia, Sorbus alnifolia, Lonicera japonica var. aueroreticulta, and Ligustrum X vicaryi. And we need to introduce new cultivars of woody landscape plants including Malus spp, Berberis spp, Sorbus alnifolia yellow autumn leaf clone etc. for the better planting design. The fruit persisting period of woody landscape plants studied by fruit name was that sorosis 276 days, samara 155 days, legume 153 days, hip 133 days, pome was 124 days, drupe 92 days, berry 73 days, capsule 67 days, follicle 55 days and nut 52 days respectively.

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오스터호프 이분법의 규명과 우리은하 벌지의 기원에 대한 새로운 해석

  • Lee, Young-Wook;Joo, Seok-Joo;Chung, Chul;Jang, Sohee
    • The Bulletin of The Korean Astronomical Society
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    • v.40 no.1
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    • pp.45.2-45.2
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    • 2015
  • 우리는 최근 현대천문학의 가장 오래된 난제로 우리은하 헤일로의 형성과 깊은 관련이 있는 구상성단계의 오스터호프 이분법이 다중항성종족 패러다임 하에서 76년 만에 완벽히 규명되는 것을 발견하였다. 또한 이 연구의 기본 개념을 우리은하 벌지에 적용한 결과, 기존 국제학계의 이론과 완전히 다른 벌지의 형성기원에 대한 새로운 해석에 도달하였다. 우리은하의 벌지에 대한 대규모 측광 서베이 분석으로부터 double red clumps가 있다는 것이 2010년에 발견되었고, 이는 디스크와 바 불안정에 기인하는 은하중심부 X-shape 구조의 증거로 널리 받아들여지고 있다. 그러나 우리는 이와 같은 국제학계의 해석이 수평계열성의 항성진화이론을 간과한데서 비롯된 허구일 가능성을 제시하고자 한다. 우리의 모델에 의하면 관측된 double red clumps는 Omega Cen을 포함하는 대다수의 구상성단에서 발견되는 것과 동일한 헬륨함량이 증가된 2세대 별들(G2)에 의한 효과이다. 우리은하 벌지에 위치한 Terzan 5 구상성단처럼, 중원소함량이 높은 벌지에서는 G2에 해당하는 수평계열성들이 광도가 약 0.5등급 더 밝은 red clump 위치에 놓이게 되어 자연스럽게 double red clumps를 형성하게 된다. 앞으로 우리의 새로운 해석이 Gaia에 의한 삼각시차 거리결정으로 확인된다면, 이는 우리은하 벌지를 이루는 대부분의 별들이 Terzan 5와 같은 윈시 빌딩블럭들의 합병과 붕괴에 의해 형성되었다는 것을 암시하여, 우리은하는 물론, 조기형은하의 형성기원 연구에 큰 전환점이 될 것으로 기대한다.

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